A record low annual mean value of total ozone was observed at Lauder, New Z
ealand in 1997, namely 294.5 DU, compared to a 1985-96 mean of 307.9+/-3.7.
Ozone values were low through most of the year, especially in winter and s
pring. These observations are similar to TOMS results for Southern mid-lati
tudes, although the long-term comparison is clouded by the change in TOMS i
nstruments. A regression analysis of the Lauder record through 1996 allows
a generally accurate prediction of the 1997 values, shows that the QBO domi
nates the 1996-97 difference, and that the 1997 values are consistent with
a linear long-term trend in ozone. The analysis does not completely explain
low monthly values in austral spring; Enhancements in biologically active
UV radiation were also observed, with monthly mean values increased by as m
uch as 20-40% from recent years. The unusual ozone values were the dominant
cause of the UV enhancement.